This invention relates to a crimping system for attaching electrical contacts to the conductive ends of wires. In particular, this invention relates to a system of the type in which the operator need only introduce the conductive end of a wire through a wire-positioning channel in order to enable a preoriented contact to be crimped to such end either in response to an operator-initiated signal or automatically.
Automatic and semiautomatic crimping systems are available from a number of different manufacturers. These include AMP Incorporated based in Harrisburg, Penn., Astro Tool Corporation based in Beaverton, Oreg., Komax based in Chicago, Ill. and Tri-Star Electronics International, Inc. based in E1 Segundo, Calif. In these systems, a number of contacts are successively cycled through a feeding mechanism so that each is aligned, in turn, with a set of crimping jaws that is included on a crimping mechanism which is also a part of each system. The operator or, in some systems, a robot arm inserts the conductive end of a wire through a wire-positioning channel in order to generally align the wire end with the prepositioned contact so that when the jaws of the crimping mechanism close, the contact is deformably attached to the conductive end of the wire.
One difficulty that has been encountered in connection with conventional crimping systems is that the wires can be inserted into the wire-receiving channel and their respective ends crimped at a faster rate than it is possible to cycle contacts through the feeding mechanism, particularly if contacts are being fed into the feeding mechanism in a loose batch so that it is necessary for the feeding mechanism to sort out the contacts and orient each contact properly. One type of feeding mechanism that has been used to sort contacts is a vibratory bowl assembly which has an upper stage connected to a contact-feeding chute. When the bowl is agitated, loose contacts inside the bowl travel along a ramped shoulder formed inside the bowl to the upper stage and then slide down the contact-feeding chute. A crimping system having a contact-feeding mechanism of this type is manufactured, for example, by Tri-Star Electronics International, Inc.
Although the present applicants are not familiar with all of the details of operation of the system just identified, in similarly designed systems, it is possible to transfer contacts from the above-described type of vibratory bowl sorter to the contact-feeding chute at a rate of about one contact every three seconds. On the other hand, it is possible for an experienced operator to manually insert wires into the wire-positioning channel and to initiate a signal (e.g., via a foot-pedal) that causes a contact to be crimped onto each wire at a rate of about one crimped contact every one and one-half seconds. Accordingly, the experienced operator is forced to pause between crimping operations in order to give the crimping system time to complete its contact processing cycle, so that less than full utilization is made of the operator's experience and skill. In conventional systems, then, the type of operation which is used can be characterized as "same-time processing" insofar as the contacts are used by the operator for the crimping operation .at almost the same time they complete their initial feeding cycle.
Another problem encountered with conventional crimping systems is the moderately high probability that a faulty crimp will occur relative to the total number of crimps that are attempted. Faulty crimps can occur, for example, when the conductive end of the wire, during its insertion, forces back the contact away from its prealigned position relative to the jaws of the crimping mechanism. When this occurs, the jaws then close about and crimp a portion of the contact that is longitudinally offset from that portion which is designed to be crimped. This type of faulty crimp is particularly likely to occur if the conductive end of the wire is formed of very fine strands, because these fine strands, even as they are being inserted through the wire-positioning channel, have a tendency to spread apart from each other in such a manner that one or more of the strands can catch on the extreme end of the contact and thereby push the contact backward. To address this particular problem, sometimes an operator will compress the individual strands by rolling them between his or her fingers, but this technique is unsuitable for those applications in which highly reliable electrical connections are needed, such as those pertaining to military-related uses, because such rolling imparts moisture, oil and other residues to the wire end that promotes rapid corrosion of the strands and that covers the end in an oxidizing film which lowers the conductivity of the resulting crimped connection.
Even if the contact remains correctly positioned relative to the jaws of the crimping mechanism, faulty crimps can still occur if the conductive end of the wire is mispositioned relative to the contact. Such mispositioning will occur, for example, if the operator fails to fully insert the wire into the wire-positioning channel prior to initiating the signal that causes the crimping jaws to close and to crimp the contact. In some instances, the contact may completely fail to attach to the conductive end of the wire so that after the operator withdraws the wire from the wire-positioning channel, the operator is then forced to remove the lodged contact either by partially disassembling the crimping unit or by extracting the contact through the channel with a contact-extracting pick. A related but somewhat different type of crimping fault can occur when stranded wire is used, because it is possible for the outer ones of the individual strands to fold back upon themselves should they happen to encounter the sides of the wire-positioning channel at too sharp an angle of approach. If a sufficient number of the strands are reflected in this manner, this can increase the cross-sectional area of the wire end to a sufficient extent as to prevent the end from entering the contact if the contact is of a small-bore type. Moreover, irrespective of whether the contact is of small-bore, large-bore or open type, these reflected strands can form barely visible conductive pigtails which stick out from beneath the crimped contact and which can short electrically to surrounding conductors, particularly if the contact is closely arranged with similar contacts in order to provide a high-density contact array.
In accordance with the foregoing, an object of the present invention, in at least preferred embodiments thereof, is to provide a crimping system that permits loose contacts to be sorted after they have entered the system and that further permits these contacts to be used for terminating wires at a faster rate than has heretofore been possible.
Another object of the present invention, in at least preferred embodiments thereof, is to prevent the occurrence of at least certain type of faulty crimps or to otherwise increase the probability of obtaining fault-free crimps.